Conventionally, there is known an actuator having a structure in which a movable table movably supported on the base is allowed to arbitrarily reciprocate depending on an objective control amount. The actuator is widely used for various conveying apparatuses, machine tools, measurement devices, industrial robots, or the like. As the actuator, there are suggested actuators of various types. Based on a difference in structure for imparting a thrust force to the movable table, the actuators can be roughly divided into two types. One of those is a type in which a drive source such as a rotary motor or a linear motor is disposed on a base to impart a thrust force from the base side to the movable table. Another of those is a type in which the drive source is mounted on the movable table to allow the movable table to travel by itself with respect to the base.
In the former type, when a plurality of movable tables having different control amounts are required, it is necessary that the drive sources in the number corresponding to the number of the movable tables be provided on the base, and it is extremely difficult that the plurality of movable tables having different control amounts exist in a single movement path on the base. Further, it is also necessary that, in an entire region of the movement path of each of the movable tables on the base, a force generated by the drive source has to be transmitted to the movable table, and when a moving range of the movable table is wide, machining of the base consumes labor and costs. In contrast, in the latter self-traveling type, the drive source itself is mounted on the movable table. Accordingly, even when the plurality of movable tables exist in the single movement path on the base, an independent control amount can be provided to each of the movable tables. Further, machining of the base becomes relatively easy. Accordingly, there is an advantage in that, even when the movement path of the movable table is long, the labor and increase in cost for machining the base can be suppressed.
However, in the latter self-traveling type, it is necessary that electric power be supplied to the drive source mounted on the movable table and a control signal corresponding to an objective control amount be supplied to the movable table. Accordingly, there is a need for connecting a power supply cable and a signal cable to the movable table. Therefore, the movable table has to be moved on the base while continuously dragging the cables. Accordingly, there is a problem in that, when the movement path of the movable table is long, the cables tend to inhibit the movement of the movable table.
On the other hand, as a so-called wireless actuator which is a self-traveling actuator having the drive source mounted on the movable table, and capable of imparting an objective control amount to the movable table without using the power supply cable and the signal cable, there is known a cargo transfer device as disclosed in JP2000-159306A. In the cargo transfer device, a linear motor is mounted on a movable fork which is provided so as to be movable with respect to a base. By driving the linear motor, the movable fork can be allowed to advance and retreat on the base in an arbitrary manner. Electric power is supplied to the linear motor on the movable fork by a non-contact power supply means provided between the base and the movable fork. Specifically, a primary side core constituting the non-contact power supply means is provided to the base, a secondary side core constituting the non-contact power supply means is provided to the movable fork, and an induced electromotive force of the secondary side core, which is generated by electrification of the primary side core, is supplied to the linear motor.